Module Name: src
Committed By: rillig
Date: Mon Apr 5 02:07:15 UTC 2021
Added Files:
src/usr.bin/xlint/lint1: ckctype.c
Log Message:
lint: warn about for wrong type cast in argument to ctype.h functions
The argument to most of the functions from <ctype.h> "shall either be
representable as an 'unsigned char' or shall equal the value of the
macro EOF".
When confronted with the infamous warning 'array subscript has type
char', there are enough programmers who don't know the background of
that warning and thus fix it in a wrong way. Neither GCC nor Clang
explain its warning to target these programmers.
Both GCC and Clang warn about 'array subscript has type char', but they
ignore the other requirements of the <ctype.h> functions, even though
these are in the C standard library.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94182
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95177
https://stackoverflow.com/a/60696378
To generate a diff of this commit:
cvs rdiff -u -r0 -r1.1 src/usr.bin/xlint/lint1/ckctype.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Added files:
Index: src/usr.bin/xlint/lint1/ckctype.c
diff -u /dev/null src/usr.bin/xlint/lint1/ckctype.c:1.1
--- /dev/null Mon Apr 5 02:07:15 2021
+++ src/usr.bin/xlint/lint1/ckctype.c Mon Apr 5 02:07:14 2021
@@ -0,0 +1,151 @@
+/* $NetBSD: ckctype.c,v 1.1 2021/04/05 02:07:14 rillig Exp $ */
+
+/*-
+ * Copyright (c) 2021 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * This code is derived from software contributed to The NetBSD Foundation
+ * by Roland Illig <ril...@netbsd.org>.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#if HAVE_NBTOOL_CONFIG_H
+
+#include "nbtool_config.h"
+
+#endif
+
+#include <sys/cdefs.h>
+
+#if defined(__RCSID) && !defined(lint)
+__RCSID("$NetBSD: ckctype.c,v 1.1 2021/04/05 02:07:14 rillig Exp $");
+#endif
+
+#include <string.h>
+
+#include "lint1.h"
+
+/*
+ * Check that the functions from <ctype.h> are used properly. They are
+ * difficult to use when their argument comes from an expression of type
+ * 'char'. In such a case, the argument must be converted to 'unsigned char',
+ * not directly to 'int'.
+ *
+ * https://stackoverflow.com/a/60696378
+ */
+
+#define NEED(cond) \
+ do { \
+ if (!(cond)) \
+ return; \
+ } while (false)
+
+static bool
+is_ctype_function(const char *name)
+{
+
+ if (name[0] != 'i' || name[1] != 's')
+ if (name[0] != 't' || name[1] != 'o')
+ return false;
+
+ return strcmp(name, "isalnum") == 0 ||
+ strcmp(name, "isalpha") == 0 ||
+ strcmp(name, "isblank") == 0 ||
+ strcmp(name, "iscntrl") == 0 ||
+ strcmp(name, "isdigit") == 0 ||
+ strcmp(name, "isgraph") == 0 ||
+ strcmp(name, "islower") == 0 ||
+ strcmp(name, "isprint") == 0 ||
+ strcmp(name, "ispunct") == 0 ||
+ strcmp(name, "isspace") == 0 ||
+ strcmp(name, "isupper") == 0 ||
+ strcmp(name, "isxdigit") == 0 ||
+ strcmp(name, "tolower") == 0 ||
+ strcmp(name, "toupper") == 0;
+}
+
+static bool
+is_ctype_table(const char *name)
+{
+
+ /* NetBSD sys/ctype_bits.h 1.6 from 2016-01-22 */
+ if (strcmp(name, "_ctype_tab_") == 0 ||
+ strcmp(name, "_tolower_tab_") == 0 ||
+ strcmp(name, "_toupper_tab_") == 0)
+ return true;
+
+ /* NetBSD sys/ctype_bits.h 1.1 from 2010-06-01 */
+ return strcmp(name, "_ctype_") == 0;
+}
+
+static void
+check_ctype_arg(const char *func, const tnode_t *arg)
+{
+ const tnode_t *on, *cn;
+
+ for (on = arg; on->tn_op == CVT; on = on->tn_left)
+ if (on->tn_type->t_tspec == UCHAR)
+ return;
+ if (on->tn_type->t_tspec == UCHAR)
+ return;
+
+ if (arg->tn_op == CVT && arg->tn_cast) {
+ /* argument to '%s' must be cast to 'unsigned char', not to '%s' */
+ warning(342, func, type_name(arg->tn_type));
+ return;
+ }
+
+ cn = before_conversion(arg);
+ if (cn->tn_type->t_tspec == CHAR) {
+ /* argument to '%s' must be 'unsigned char' or EOF, not '%s' */
+ warning(341, func, type_name(cn->tn_type));
+ return;
+ }
+}
+
+void
+check_ctype_function_call(const tnode_t *func, const tnode_t *args)
+{
+
+ NEED(func->tn_op == NAME);
+ NEED(is_ctype_function(func->tn_sym->s_name));
+ NEED(args != NULL);
+ NEED(args->tn_left != NULL);
+ NEED(args->tn_right == NULL);
+
+ check_ctype_arg(func->tn_sym->s_name, args->tn_left);
+}
+
+void
+check_ctype_macro_invocation(const tnode_t *ln, const tnode_t *rn)
+{
+
+ NEED(ln->tn_op == PLUS);
+ NEED(ln->tn_left != NULL);
+ NEED(ln->tn_left->tn_op == LOAD);
+ NEED(ln->tn_left->tn_left != NULL);
+ NEED(ln->tn_left->tn_left->tn_op == NAME);
+ NEED(is_ctype_table(ln->tn_left->tn_left->tn_sym->s_name));
+
+ check_ctype_arg("function from <ctype.h>", rn);
+}
